Valve mechanism operated by a plurality of thermostats



Feb. 26, 19 N. P. M KENZIE VALVE MECHANISM OPERATED BY A PLURALITY OF THERMOSTATS Filed Aug. 16, 1948 IN V EN TOR. Nvz'lle P fllclfenzte.

BY Camww-n; MM fjm' Afitor Ref/S Patented Feb. 26, 1952 VALVE MECHANISM OPERATED BY A PLURALITY OF THERMOSTATS Neville P. McKenzie, Knoxville, Tenn., assignor to Robertshaw-Fulton Controls Company, Knoxville, Tenn., a corporation of Delaware Application August 16, 1948, Serial No. 44,518

Claims.

which are that such devices do not provide positive connections between the several thermostats and the valve for both directions of valve movement so that under certain circumstances one or more of the thermostats may lose control of the valve because of the position to which the compound lever system has been moved by one or more of the other thermostats.

It is an object of this invention to provide an improved valve mechanism operable by a plurality of thermostats through a compound lever system wherein each thermostat may exert a positive control of the valve at all times, whether the temperature be rising or falling and whether the valve is to be opened or closed.

Another object of this invention is to provide an improved device of the type characterized wherein each thermostat has at all times a positive controlling relationship with the valve so that the valve is always responsive to the control of each thermostat irrespective of the action of any other thermostat on the compound lever system.

Another object of this invention is to provide an improved device of the type characterized in which all of the thermostats act through the compound lever systems to move the valve in the same direction on rising temperatures or on falling temperatures.

Another object of this invention is to provide an improved device of the type characterized which includes provisions for line adjustment so that the composite effect of the thermostats on the valve can be nicely predetermined.

Another object of this invention is to provide an improved device of the type characterized which can be embodied in a pilot valve mechanism disposed in any desired relationship to a pressure operated device to be controlled thereby so as to facilitate installation and access for inspection or repairs.

Another object of this invention is to provide an improved device of the type characterized which is of simple and compact construction so that it may be readily installed as a unit at convenient locations.

Another object of this invention is to provide an improved device of the type characterized which is highly eflicient in sensitively responding to small temperature variations.

Other objects will appear as the description of the invention proceeds.

- The invention is capable of receiving a variety of mechanical expressions only two of which have been illustrated on the accompanying drawing, and therefore it is to be expressly understood that the drawing is for purposes of illustration only and is not to be construed as a definition of the limits of the invention, reference being had to the appended claims for that purpose.

Referring drawing,

Fig. 1 shows somewhat diagrammatically a thermostatically operated pilot valve embodying the present invention; and

Fig. 2 is a fragmentary view to illustrate the embodiment of Fig. 1 provided with a thermostatic adjustment of a fulcrum.

The invention may be applied to a wide variety of pressure operated devices using a liquid, gas or other suitable fluid as the pressure controlling medium. As the pressure operated device forms no part of the present invention it has not been illustrated on the drawing, but, by way of illustration, it may be a pressure operated valve for controlling the flow of a heating or a cooling medium. However, it is to be expressly understood that the present invention may be applied not only to the control of any suitable pressure operated valve, but also to the control of any other suitable pressure operated device. While the present invention possesses particular utility when incorporated in a pilot valve mechanism, and will herein be exemplified by such an application, it is also to be understood that, as respects some of the broader aspects of the invention, other suitable valves may be controlled by the thermostatically actuated compound lever system of the present invention.

In the form shown, [0 designates a pilot valve housing of any suitable form, construction and in detail to the accompanying 'material and having suitably secured thereto an inlet nipple I I for communication with any suitable source of fluid under pressure and an outlet nipple I! for communication with any suitable pressure operated device. Interiorly said housing I0 is provided with a chamber l3 with which communicates a passage l4 leading from the inlet IS in nipple ll. Mounted in said chamber 53 in any suitable way is a valve seat member 16 of any suitable construction and providing a valve port l1. Cooperating with the valve seat i8 provided by member I6 is a pilot valve memher, here illustrated as having a generally hemispherical seatlng portion ill at its end which is cooperatively associated with the valve seat l8 and, at its opposite end, a generally spherical seating portion for a purpose to be explained. Pilot valve member i9, 20 has a passage 2| ex tending therethrough from one end to the other provide a bleed opening.

hermetically sealed in any suitable way to the end ll! of said pilot valve member is an expansible and collapsible corrugated tubular Wall or bellows 22 which, at its opposite end, hermetically sealed to a ring 23 adapted to seat on a shoulder 224 provided near the outlet end of the chamber 53. Ring 23 is secured on shoulder 24 by an exteriorly threaded thimble member 25 received in threaded opening '25 at the outer end of the chamber 513. Thimble member 25 has a passage extending therethrough leading to and through iipple 28 designed to be connected in any suitle way to a relief or drain passage. Reacting etween the thlmble member 25 and the pilot valve member, and disposed interiorly of the bellows 22, is a coil spring 29 which normally urges the end it of said pilot valve member into engagement with its seat l8.

hermetically sealed in any suitable way to the inner face of housing is is the stationary end of an expansible and collapsible corrugated tubular wall or bellows 30 having integral therewith or suitably attached thereto a movable end wall which is hermetically sealed to the shoulder 32 of a block 33 which, at its inner end, is provided with two recesses 34 and 35 of different size so to provide a shoulder therebetween that forms valve seat til for cooperation with the spherical end 20 of the pilot valve member. Bellows ill with its movable end ill provides an expansible collapsible chamber which is in communication "with. the valve port ll, and housing ill is also provided with a second passage 3t that leads from said chamber ill to the outlet 35 in nipple l2. Cooperating with the movable end wall at of chamber 3'! is a coil spring til of greater stiffness than the before mentioned spring 29, said spring ll) reacting between said movable end wall 3i and an abutment plate ll suitably shaped to form a spring seat and supported and retained in any suitable way on a rectilinearly movable pin '12. As shown said pin is slidably mounted in an aperture 43 provided in any suitable member 44 attached to or integral with the wall of a casing t5 which constitutes a housing for the compound lever system to be described. The pilot valve housing ill is shown as mounted in an aperture 46 of said casing Q5 and secured therein in any suitable way, and housing ill may be threaded at M to receive a depending annular member or skirt 38 which surrounds the expansible and collapsible chamber ill in protective relationship thereto.

Pin 32 is slidable rectilinearly under the control of a lever 50 here shown as having a threaded post 5| received in a threaded collar 52 adjacent one end thereof so that the effective length of the connection between the lever and the abutment plate M can be nicely adjusted when setting up the compound lever system to be described, or the threads may be formed on the end of the pin d2. lever 50, intermediate its length, is provided with a suitable fulcrum recess and at its opposite end said lever till is pivotally connected by any suitable pivot pin 54, with a second lever 55 fulcrumed on a stationary part within the casing 45. The fulcrum of lever 55 is preferably adjustable, and to this end lever 55 is shown as provided with a cylindrical member 51, having a threaded aperture 58 extending therethrough, and in engagement with a stationary fulcrum member 56 carried by the casing 45 in any suitable way. Mounted in said aperture 58 is a bolt 59 having a head 50, said bolt passing through an aperture in a transverse ear ill on the lever 55. Interposed between said ear Bi and the cylindrical member 51 is a coil spring 62 which holds the head 550 of the bolt 59 against said ear 5|. By rotating the bolt 59 the cylindrical fulcrum member 51 may be moved toward or away from the ear Bl thereby adjusting its line of contact on fulcrum -63 with respect to the length of lever 55. Lever 55 also has a lateral projection 54 and pivotally mounted thereon by means of a pivot pin 65 of any suitable construction is a third lever 66 to be referred to more fully hereinafter.

Cooperating with the fulcrum recess 53 in lever E50 is the end of a post "in which passes slidably through an aperture H in an end block 12 and is secured in any suitable way to the movable end wall ll of an expansible and collapsible chamber l3 constituting a motor vessel whose inner periphery is formed by an expansible and collapsible corrugated tubular wall or bellows l4 and whose outer periphery is formed by a tubular member l5 hermetically sealed at one end to said end blocl: l2 and hermetically sealed at its opposite end to a cap l5. One end of bellows i4 is her -ietically sealed. to said end block 12 and its opposite end has formed thereon or suitably attached thereto said movable end wall ll to which the post '10 is secured. Casing d5 is shown as provided with a neck-like portion "it into which the outer cylindrical wall l5 of said chamber "is is projected by securing the cap V6 in any suitable way to the end of said neck-like portion, in which position the inner end of post Bill is engaged in the fulcrum recess 53 of lever to. Communicating with said expansible and collapsible chamber i3 is a conduit ill of any suitable size, length and construction, and either rigid or flexible as desired, said conduit ill in turn being in communication with the interior of a bulb ill] of any suitable construction and character which may be mounted in position at any suitable location and in any suitable way as by means of a mounting nut 8|. Bulb 80, conduit l9 and said expansible and collapsible chamher it are charged with any suitable thermosensitive fluid, preferably a liquid solidly filling said bulb, chamber and communicating conduit, so that variations of temperature at the bulb will cause expansion or contraction of said chamher "it and thereby, through the movement of end wall ll, cause the post ill to move lever 50 about its pivot 54 acting as a fulcrum. By Way of illustration, the bulb bl) may be subjected to the temperature of a heating or a cooling medium.

lPivotally connected to the lever 66 at 83 and 84 adjacent its opposite ends are posts 85 and 86 which extend slidably through apertures 81 and 538 in end blocks 89 and 80 carried by tubular memhers ill and 92 which extend through apertures 553 and 94 in the casing Q5 and are hermetically sealed to cap members 95 and 98 secured to the exterior of the casing 35 in any suitable Way. Hermetically sealed to the end blocks 89 and are expansible and collapsible corrugated tubular walls or bellows 91 and 98 having, integral therewith or suitably secured thereto, movable end Walls 99 and I to which the posts 85 and 06 are respectively secured. Bellows 91 and 98, together with their surrounding tubular members 9| and 92, form expansible and collapsible chambers WI and I02 constituting motor vessels. Communicating with said last named chambers are conduits I03 and I04 of any suitable size, length and construction, and which may be either rigid or flexible as desired, which in turn lead to bulbs I05 and I06 of any suitable construction and mounted in position in any suitable way. Each of said bulbs, together with its communicating conduit and expansible and collapsible chamber, is charged with a suitable thermosensitive fluid, the bulb, conduit and communicating chamber preferably being solidly filled with a liquid. Bulb I05 may be, by way of illustration, an outdoor bulb, while bulb I00 may be an indoor bulb subjected to the temperature of the space whose temperature is to be controlled by use of the circulating medium to which bulb 80 is subjected.

It is to be understood that the bulbs 80, I05 and I06 may be disposed at any suitable distances away from the casing 45, depending upon the temperatures to which said bulbs are to be subjected, and it is also to be understood that the casing 45 with its associated thermostats may be disposed at any suitable distance from the pressure operated device in communication with the outlet 39 as well as the source of pressure fluid communicating with the inlet I5.

If desired, the device as so far described may also be provided with a limit switch, as for ex ample to open the motor circuit of a pump when one or more of the thermostats have reached a limit position. As illustrated, an extension lever I I0 is pivoted intermediate its ends on the casing 45 and one end thereof is pivotally connected to the lever 66. The other end of the extension lever IIO carries a switch operating post III so that when lever 66 is moved to a predetermined extent in a clockwise direction around its fulcrum wit-h resultant counterclockwise rotation of the extension lever IIO, post III will engage the actuator II2 of any suitable switch II3, having leads II4, secured to the wall of the casing 45 in any suitable way.

In the embodiment of Fig. 1 the fulcrum member 51 of lever 55 is manually adjustable by manipulation of the bolt 59. If preferred, however, said fulcrum may be made automatically adjustable as shown in Fig. 2. As here shown somewhat diagrammatically the fulcrum member of lever 55 is in the form of a roller II5 pivotally mounted at I IS on a post I I1 extending from the movable end wall II8 of an expansible and collapsible chamber II9 formed between an outer tubular member I20 hermetically sealed to an end block I2I and to a cap member I22 and an expansible and collapsible corrugated tubular wall or bellows I23 whose stationary end is hermetically sealed in any suitable way to the end block I2I and whose movable end has formed thereon or suitably secured thereto said movable end wall Il8. Communicating with said chamber I I9 is a conduit I24 of any suitable size, length and construction, and which may be flexible or rigid as desired, that leads to a bulb I25 of any suitable construction and which may be mounted in any suitable way at any suitable location.

Assuming that the inlet I5 is connected with a suitable source of fluid pressure and that outlet 39 is connected with any suitable pressure operated device, upward movement of the pin 42,

as viewed in the drawing, will compress spring 40 and collapse chamber 31 against the tension of spring 29 as soon as the pressure of spring 40 is great enough to overcome any pressure in chamber 31 and the tension of said spring 29. The block 33 carried by the movable end wall 3I of said chamber 31 will thereby exert a thrust on the pilot valve member I9, 20, to lift its end portion I9 off of the seat I8. Fluid under pressure will now flow through the inlet I5, passage I4, chamber I3, port I1, chamber 31, passage 38 and outlet 39 to the pressure operated device, to build up fluid pressure therein. Pressure actuation of said device may open or close a valve or otherwise move a pressure responsive member depending upon the function to be subserved. As the pressure builds up in said pressure operated device it will also build up in the chamber 31, expanding said chamber against the tension of spring 40 and permitting the spring 29 to move the portion I9 of said pilot valve member back into engagement with its seat I8 as soon as a predetermined pressure is built up in chamber 31. As the end 20 of said pilot valve member is in engagement with its seat 36 throughout such movements, the fluid under pressure cannot escape from the chamber 31 when valve portion I9 engages its seat I8, and therefore the pressure is maintained in the chamber 31 and the pressure operated device in communication therewith, and equilibrium is established.

If pin-42 is moved downwardly as viewed in the drawing, the tension on the spring 40 is released and the pressure in chamber 31 causes the movable end wall 3I to move downwardly as viewed in the drawing, moving the valve seat 36 away from the portion 20 of the pilot valve member. Thereupon the pressure in said chamber 31 may bleed out through the passage 2| to the relief or drain passage in communication with the passage 21. As soon as the pressure in chamber 31 is reduced to the point where spring 40 can move movable end wall 3| upwardly as viewed in the drawing, because of the reduced pressure in chamber '31, valve seat 33 re-engages the spherical portion 20 of the pilot valve member, preventing further escape of fluid and reestablishing the equilibrium.

Therefore, whether the pin 42 is moved upwardly or downwardly as viewed in the drawing the pilot valve member is positively actuated to admit pressure to or relieve pressure from chamber 31 and thereby eiTect actuation of the pressure operated device, following which equilibrium is i e-established and the existing pressure in the chamber 31 maintained until the next movement of the pin 42.

If the temperature at the bulb 60 increases the pressure in chamber 13 is increased, expanding said chamber and moving the movable end wall 11 upwardly as viewed in the drawing. Such movement of said movable end wall is transmitted through post 10 to the lever 50 which fulcrums around the pivot pin 54 in an anticlockwise direction to move the pin 42 upwardly .xs viewed in the drawing. Conversely, a decrease of temperature at the bulb will cause a movement of the pin 42 downwardly as viewed in the drawing.

If the temperature at the bulb I05 increases the pressure in chamber I01 is increased, causing said chamber to expand and move the movable end wall 99 downwardly as viewed in the drawing. This movement of said movable end wall is transmitted through post to the lever asscsm 66 which fulcrums on pivot pin 84, causing said lever with its pivot pin 65 to move in a clockwise direction. Lever 55 being iulcrumed at 63, such clockwise movement of the pivot pin 65 causes a clockwise movement of lever 55 and its pivot pin 54, and lever 50 is thereby moved in an anticlockwise direction about its fulcrum 53 to cause the pin 42 to move upwardly as viewed in the drawing. Conversely, a decrease in temperature at the bulb I05 will cause the pin 42 to move downwardly as viewed in the drawing.

Increase of temperature at the bulb I05 will cause an increase of pressure in the chamber I02 expanding said chamber and causing the movable end wall I to move downwardly as viewed in the drawing. Such movement of said movable end wall moves the post 86 downwardly as viewed in the drawing, causing the lever 66 to fulcrum about pivotpin 83. Such movement of the lever 66 in an anticlockwise direction causes pivot pin 65 to move in an anticlockwise direction, and as lever 55 is iulcrumed at 63 the pivot pin 54 is moved in a clockwise direction about said fulcrum 63. Such movement of pivot pin 54 causes lever 50 to fulcrum at 53 in an anticlockwise direction moving the pin 42 upwardly as viewed in the drawing. Conversely, decrease in temperature at the bulb I06 will cause pin 42 to move downwardly as viewed in the drawing.

It will therefore be observed that an increase of temperature at any of the bulbs causes the pin 42 to move upwardly, while a decrease of temperature at any of the bulbs causes the pin 42 to move downwardly, as viewed in the drawing. Suchupward and downward movements of the pin 42 cause positive actuation of the valve member as hereinabove explained. Therefore, not only are all movements of the compound lever system transmitted positively to the valve member, whether the latter is moved in a valve opening or a valve closing direction and whether the initiation of movement is due to an increase or a decrease of temperature, but all of the thermostats are effective to produce movement of the valve member in the same direction for an increase of temperature or for a decrease of temperature. Hence each thermostat is at all times operatably connected to the valve mechanism and eifective to move said valve mechanism in the proper direction, depending upon the direction of temperature change, and at no time is a thermostat disconnected from the valve mechanism so that a change of temperature at such thermostat will be ineffective to obtain the proper response of the valve mechanism. 1

The relative effects produced by the respective thermostats can be nicely proportioned by appropriate determination of the lengths of the lever arms, or the working characteristics of the respective thermostats, or both. Furthermore, the effects of the thermostats including bulbs I05 and I06 on the compound lever system may be finely adjusted by adjusting the fulcrum of lever 55. This is done in the embodiment of Fig. 1 by rotating the bolt 59 so as to vary the position of fulcrum line 63 with respect to the pivots 65 and 54 or, in the embodiment of Fig. 2, this same result may be obtained automatically by the adjustment of the fulcrum line 63 through movement of the roller H5 from the movable end wall II8 of the expansible and collapsible chamber H9 constituting a part of the thermostat whose bulb I may be subjected to any appropriate temperature for determining such adjustment.

It will further :be observed that when the invention is embodied in a pilot valve mechanism, such mechanism and its associated parts may be disposed in any convenient location and at any desired distance away from the pressure operated device to be controlled, and at the same time the bulbs of the several thermostats may be disposed at relatively remote points from the pilot valve mechanism so as to be properly subjected to the several temperatures to which they are intended to respond.

Thus a highly efficient and sensitively adjustable automatic valve mechanism has been provided which includes a compound lever system under the control of a plurality of thermostats enabling its application to various services but possessing marked advantages when used as an automatic pilot valve mechanism to control the admission and release of pressure to and from pressure operated devices of various character and form.

While the embodiments of the invention illustrated on the drawing have been described with considerable particularity, it is to be expressly understood that the invention is not limited thereto, as the same is capable of receiving a variety of mechanical expressions, some of which will now readily suggest themselves to those skilled in the art, while changes may be made in the details of construction, size, arrangement, proportion, etc., and parts may be replaced by equivalent parts, without departing from the spirit of this invention. Reference is therefore to be had to the appended claims for a definition of said invention.

What is claimed is:

1. In a thermostatically operated valve mechanism having a housing providing a valve seat and a valve member cooperating with said seat, means for operating the valve comprising a rectilinearly movable member operatively connected to said valve member, three thermostats for subjection to different sources of temperature variation and each including an expansible and collapsible chamber having a movable end wall, a compound lever system operatively connected to said reciprocating member and including three levers, means for positively transmitting the movements of one of said movable end walls to one of said levers which is operatively connected to said reciprocating member, a pair of members operatively connected to two other movable end walls and pivotally connected to a second lever of said system for positively transmitting the movements of said other end walls to said second lever, and

pivotal connections between the third lever of said \system and both of said first and second named levers, said third lever :being fulcrumed on said housing.

2. In a thermostatically operated valve mechanism having a housing providing a valve seat and a valve member cooperating with said seat, means for operating the valve comprising a rectilinearly movable member operatively connected to said valve member, a plurality of thermostats for subjection to different sources of temperature variation and each including an expansible and collapsible chamber having a movable end wall, a compound lever system operatively connected to said reciprocating member and including three levers, means for positively transmitting the movements of one of said movable end walls to one of said levers which is operatively connected to said reciprocating member, said means constituting a fulcrum for said lever, a pair of memoers operatively connected to two other movable end walls and pivotally connected to a second lever of said system for positively transmitting the movements of said other end walls to said second lever, and pivotal connections between the third lever of said system and said first and second named levers, said third lever being fulcrumed on said housing.

3. In a thermostatically operated valve mechanism having a housing providing a valve seat and a valve member cooperating with said seat,

means for operating the valve comprising a rectilinearly movable member operatively connected to said valve member, a plurality of thermostats for subjection to different sources of temperature variation and each including an expansible and collapsible chamber having a movable end wall, a compound lever system operatively connected to said reciprocating member and including three levers, means operatively connecting one of said movable end walls to one of said levers one end of which is operatively connected to said reciprocating member, and a pair of members operatively connected to two other movable end walls and pivotally associated with a second lever'of said system, the third lever of said system being pivotally connec ed to the other end of saidfirst lever and to said second lever at, a point intermediate the connections of said'p'airof members thereto and said third lever having a fulcrum on said housing so that the expansion of all of said chambers transmitted through said lever system to said reciprocating member moves said reciprocating member in the same direction. I

4. In a thermostatically operated valve mechanism, in combination with a housing providing a valve seat, a valve member cooperating with said seat and a rectilinearly movable member operatively connected to said valve member, a plurality of thermostats for subjection to difierent sources of temperature variation and each including an expansible and collapsible chamber having a movable end wall, a compound lever system operatively connected to said reciprocating member and including three levers, means operatively connecting one of said movable end walls to one of said levers, and a pair of members operatively connected to two other movable end walls and pivotally connected to a second lever of said system for positively transmitting the movements of said other end walls to said second lever, the third lever of said system being so pivotally connected to said first and second levers that the expansion of all of said chambers transmitted throu h said lever system to said reciprocating member moves said reciprocating member in the same direction, said operative connection between said valve member and said reciprocating member including resilient means interposed therebetween for retaining said reciprocating member at all times in positive engagement with one of said levers and for transmitting the movements of said reciprocating member to said valve member.

5. In a thermostatically operated pilot valve mechanism, a valve housing provided with an inlet, an outlet and a'relief passage, an expansible and collapsible chamber associated with said housing and having a movable end wall, a ported valve seat in said housing through which said chamber communicates with said inlet, said chamber also having means of communication with said outlet, a valve seat member mounted on said movable end wall, a pilot valve member having two seating portions for respective oooperation with said ported seat and said valve seat member and having a bleed opening therethrough in communication with said relief passage, resilient means cooperating with said movable end wall in opposition to the pressure in said chamber on said wall, means for increasing and decreasing the tension of said resilient means to effect movement of saidmovable end wall in one direction or the other including a reciprocating member, a compound lever system operatively connected to said reciprocating member, and a plurality of thermostats operatively connected to the levers of said system.

6. In a thermostatically operated pilot valve mechanism, a valve housing provided with an inlet, an outlet and a relief passage, an expansible and collapsible chamber associated with said housing and having a movable end wall, valve seats in said housing through which said chamber communicates with said inlet and said relief passage, a pilot valve member in said chamber cooperating with said valve seats and operable from said movable end wall, opera ive connections for applying pressure to and relieving pressure on said movable end wall including a spring acting on saidmovable end wall and bracing the same in opposition to the action of the internal pressure thereon, a reciprocating member for varying the tension upon said spring, a compound lever system including a lever operatively connec ed to said reciprocating member, a second lever pivotally connected to said first lever, a third lever pivotally connected to said second lever, a plurality of thermostats each including an expansible and collapsible chamber having a movable end wall, and members operatively connected to said movable end walls and pivotally associated with said levers, said spring being effective to bias said first lever into operative engagement with that one of said members with which it is associated.

'7. In a thermostatically operated pilot valve mechanism, a valve housing provided with an inlet, an outlet, and a relief passage, an expansible and collapsible chamber associated with said housing and having a movable end wall, valve seats in said housin through which said chamber communicates with said inlet and said relief passage, a pilot valve m mber in said cham er cooperating with said valve seats and operable from said movable end wall, a compression spring having one end operatively connected to said movable end wall for a plying pressure thereto and relieving pressure thereon and bracing said wall in opposition to t e action of internal pressure thereon, a reci rocating member engaging the other end of said spring for varying its tension, a compound lever system operatively connected to said reciproca ing member and including three levers, a plurality of thermostats for sub ection to difierent sources of tem erat re variation, means for positively transmit ing the movement of one of said thermostats to one of said levers which is operatively connected to said reciprocating member, a pair of members operatively connected to two other thermostats and pivotally associated with a second lever, and pivotal connections between the third lever and both of said first and second levers, said third lever having a fulcrum on the housing.

8. In a thermostatically operated pilot valve mechanism, a valve housing provided with an inlet, an outlet,-and a relief passage, and expansible and collapsible chamber associated with said housing and having a movable end wall.

' ll valve seats in said housing through which said chamber communicates with said inlet and said relief passage, a pilot valve member in said cham ber cooperating with said valve seats and. operable from said movable end wall, a compression spring having one end, operatively connected to said movable end wall for applying pressure thereto and relieving pressure thereon. and bracing" said wall in opposition to the action of internal pres sure thereon, a reciprocating member engaging the other end o'i said spring for varying its bl-Ell sion, a compound lever system. operatlvelv core nected. to said reciprocating member and includ ing three levers, a plurality of thermostats for subjection to different eources ct" temperature variation, means. operatlvelt connecting one of said thermostats to one of said. levers one end. of which is operativel connected. said recipmeeting: member, and pair of members opera tlvelrl' connected. to two other thermostats; and plvotally associated with a second lever, the third lever being; pivotall v cormect to the other end d l rough member moves the s lover .a latte in. th r to :a t,. .osta bovine: M H a valve met "or operating 1e me l 4 of WW 0, system opera 'v connected to at and including three lever; pi.vota" v coune operatlvely cmmected to or wallet and. pivotal lev wn on operr connected to ciprocatme member, a plurality membe s on erativeb JG c 'va' a iai ll till said levers for positively transmitting movements cl said other end walls to said second lever, and an adjustable fulcrum on said housing. for the third. of said levers to vary the proportional eflect or the movement of said movable end walls on said reciprocating member.

10. In a thermostatically operated valve mech-- anism. having a housing providing a valve seat and a valve member cooperating with said means for operating the valve comprising a rectillnearltv movable member operatively connected to said valve member, a plurality of thermostatsfor subjection. to difierent sources of temperature variation and. each including an expansible and collapsible chamber having a movable end wall! a compound lever system operatively connected to said reciprocating member and including three levers pivotally connected together, a member operatlvely connected to one of said movable end V walls and pivotally associated with one of said levers which is operatively connected to said re ciprocating membern members operatlvely con nected. to two other movable end walls and pivotal'iy associated with the second of said levers,

\= an adjustable fulcrum. on; said housing for the third of said levers for varying the proportional reciprocating member, and tlrrermo' operattvelr connected to :ior adjusting the position NEWLQLh Pu REFERENQES CI'llTF'tl Putt-g June 13, Henney et Aug 1, mm

Spence m May 12, Utto Nov. ill,

U 2, ii, a ammond et al. c- M l6, "o W Mar, 29,, 

